Objectives and Specific Aims Myocardial ischemia and infarction with resultant adverse ventricular remodeling and heart failure form an increasingly prevalent global health problem for which medical and surgical treatments are limited. Innovative therapies are greatly needed. This proposal seeks to investigate and develop a novel acute endogenous revascularization therapy which upregulates endothelial progenitor cells (EPCs) and specifically targets them to ischemic myocardium. This post- infarction angiogenic therapy to augment myocardial microcirculation will study three specific aims: 1) Mobilization and targeted chemokinesis of EPCs to revascularize ischemic myocardium. 2) Angiogenic reengineering of regional myocardial biomechanical properties to attenuate adverse ventricular remodeling and improve cardiac function. 3) Translational preclinical large animal model testing of endogenous revascularization therapy utilizing progressively less invasive, clinically-available technologies. Research Design and Methods: In a rat model of myocardial infarction and ventricular remodeling, bone marrow production of EPCs will be stimulated with granulocyte macrophage colony stimulating factor (GMCSF). The upregulated EPCs will be targeted to the ischemic heart with direct intramyocardial administration of the potent EPC chemokine stromal cell derived factor-11 (SDF). Specific mechanisms will be elucidated by ex vivo tagged EPCs as well as an extracardiac SDF decoy. EPCs will be tracked with flow cytometry and immunohistochemistry. Angiogenesis will be quantified with lectin microangiography. The impact of microrevascularization on ischemic myocardial contractility will be determined with dobutamine stress echocardiography and myocardial tissue properties will be studied utilizing atomic force microscopy and tensile strength measurements. Ventricular remodeling and myocardial function will be assessed at multiple time points with echocardiography and an intracavitary pressure-volume conductance microcatheter. A well-established ovine model of ischemic heart failure will be utilized to study the efficacy of SDF/GMCSF therapy in a clinically translatable animal model. A stepwise evaluation of progressively less invasive, clinically available delivery technologies, from minimally invasive thoracotomy to Stiletto endocardial injection catheter to percutaneous intracoronary administration, will be undertaken to optimize cytokine delivery. PUBLIC HEALTH RELEVANCE: Heart attack and its complications comprise a global health problem for which there are few highly effective treatments. As an innovative therapy, this proposal seeks to amplify the body's native repair machinery by stimulating vascular progenitor cells in the bone marrow and then specifically directing them to the heart to grow new perfusing blood vessels to the damaged heart muscle and providing a clinically viable treatment for human disease.